The invention relates generally to cover structures of electrical devices where two cover parts are intended to be movable in relation to each other. Particularly the invention relates to such a structure where further an electrical contact must be arranged between the different parts of the cover structure.
Small-sized electronic devices which are intended to be easily portable by a person often have a transport position and an operating position. As an example we examine a mobile phone 100 provided with a telescopic cover according to the FIG. 1. For transport the lower part 101 of the cover is in a position shown in the figure by a continuous line. For operation it can be slid in the direction of the arrow into the position 101xe2x80x2 shown by the broken line, whereby the distance between the microphone 102 an d t he speaker 103 better corresponds to the distance between the mouth and ear of a typical user.
In the mobile phone of FIG. 1 the microphone 102 is located in the movable lower part of the cover. There are also known mobile phones where the speaker is located in a part which can be moved in relation to the rest of the mobile phone. Such structures are characterised in that there must be an electrically conducting connection between the mutually movable parts. Often very stringent requirements are placed on the electrical characteristics of the connection. For instance in the structure of the FIG. 1 the microphone 102 must operate equally well irrespective of the mutual positions of the cover parts, and the function must remain unchanged irrespective of a high number of cover opening and closing, operations.
FIG. 2 shows a known cover structure which can be used to realise an electrically conducting connection for the microphone in a structure according to the FIG. 1. The structure comprises a cover part 201 and a microphone bracket 202. The microphone 203 is mounted between the cover part and the bracket so that its sound sensitive spot is aligned with the hole 204 in the cover. Before the microphone is mounted it is soldered to conductor areas on the surface of a flexible printed circuit foil 205 or a so called flex. The flex further comprises an elongated section and on its surface parallel elongated conductor areas 206 and 207, from which there is a connection to the microphone. The elongated section of the flex is glued to the inner surface of the cover part, so that the conductor areas 206 and 207 are left visible. The microphone bracket 202 is fastened over the microphone, for instance by ultrasonic welding of its edges to the inner surface of the cover part. Isolating rings 208 and 209 are used in order to isolate the microphone from mechanical vibrations of the cover. When the cover assembly is finished it is attached to the mobile phone by guide bars 210. The mobile phone must have two parallel contact springs which are pressed against the elongated conductor areas 206 and 207 and which form the electrical connection from the microphone to other electrical parts of the mobile phone.
Disadvantages of the structure presented in FIG. 2 are i.a. the required ultrasonic welding or some other fastening step, which is relatively complicated to realise, and the high accuracy of the positioning, which is required for fastening the flex at the exactly correct position. Further, the elongated conductor areas of the flex must be coated by some method which ensures a high mechanical wear resistance and an excellent electrical contact, irrespective of the position the telescopic cover of the mobile phone. The cost of the coating in the known solutions is up to 80 % of the total manufacturing costs of the flex.
The object of the present invention is to present a structure of the telescopic cover of an electrical device which is advantageous regarding the assembly. A further object of the invention is to present a structure where the electrical connection between two mutually movable cover parts can be realised advantageously and reliably.
The objects of the invention are attained by using a two-layer structure in the movable cover part, so that the parts of the movable cover part are attached to each other by form-fitting joints and at the same time act as a holder for electrical components placed between them. The inner layer of the cover structure acts as a bracket for the slide conductors which form the electrical contact between the mutually movable parts.
The structure according to the invention is characterised in that it comprises an outer cover part and an inner cover part of substantially the same size, whereby a certain electrical component is located between the outer cover part and the inner cover part, and slide conductors on such a surface of the inner cover part which is not against the outer cover part.
According to the invention the movable cover part of the electrical device comprises an outer cover part and an inner cover part which are fastened to each other, most preferably by a form-fitting joint. The cover parts can be shaped so that spaces exactly of a desired size and shape are left between them for electrical components or for other separately mounted components, whereby no separate brackets are required for these components.
In order to form the electrical contact between the movable cover part and some other part there are used slide conductors which are fastened to the inner cover part. They can be made of a flexible printed circuit foil or of separate metal strips. The slide conductors can also be made into the inner cover part as so called inserts if extrusion or a corresponding method is used to manufacture the inner cover part. If the slide conductors are located separated from such electrical components which must have an electrically conducting connection from the conductors, then a conductor component made of a flexible printed circuit foil or any other suitable material can be located between the cover parts so that it forms the required electrical connections.
Thanks to the invention the movable cover part of the electrical device can be assembled even totally without soldering, ultrasonic welding or other operating steps which are difficult to automate, and this is particularly advantageous regarding the assembly. If the slide bars are made of separate metal strips it is possible to use such advantageous coating methods which ensure wear resistance and a good electrical contact, which methods are not suitable for a flexible printed circuit foil. Then substantial savings are obtained in comparison to the coating of a prior art flexible printed circuit foil.